1Fill a large pot with lightly salted water and bring to a rolling boil. Stir in rotini, and return to a boil. Cook uncovered, stirring occasionally, until rotini has cooked through, but is still firm to the bite, 10 to 12 minutes. Drain and rinse with cold water.
2Transfer pasta to a large bowl.
3Toss salmon and cucumber in with rotini, flaking the salmon as you stir.
4Combine Greek yogurt, mayonnaise, dill, and onion powder in a small bowl.
5Spoon yogurt mixture over rotini and gently combine.
6Chill in the refrigerator for at least 30 minutes.
7Arrange slices of Roma tomatoes on the salad before serving.
1 (13.25 ounce) package dried whole wheat rotini pasta